Machines of this kind, which operate in a manner reminiscent of gear pumps, formed part of the art since the time of the first World War. Exemplary in this respect is British Patent Specification No. 117,097, which discloses two pairs of gears, two on each shaft, arranged axially in side-by-side relationship with a groove therebetween through which there is introduced a cable which is then coated with rubber advanced through gear pumps on each side thereof.
In material processing machines of this kind, an elastomer is initially introduced as cut portions into the teeth interspaces, where the tips of the gear teeth slide against the inner wall of the housing, and carried forward to the tooth engagement, where treatment of the elastomer first commences. In order to work the elastomer more thoroughly and to obtain improved sealing conditions, applicant has previously proposed the use of gears which are provided centrally with radial grooves into which a tongue projects in a direction opposite to the direction of rotation. This is described in European Patent Specification No. 81850055,3/0062017. In this way, the pressure created where the teeth of the gears meet, or the tooth meshing point, will be propagated backwards via the radially extending grooves, to sealing devices inserted therein. The sealing devices, and also the tongue, can be adjusted to control leakage, thereby enabling control of the extent to which the elastomer is worked.